Sanitary napkin with knitted wrapper



Sept' 5, 1967 E. A. MORSE 3,339,549

SANITARY NAPKIN WITH KNITTED WRAPPER Filed Nov. 2, 1959 United States Patent O 3 339,549 SANITARY NAPKIN WITH KNITTED WRAPPER Edward A. Morse, Fanwood, NJ., assiguor, by mesne assignments, to Johnson & Johnson, New Brunswick, NJ., a corporation of New Jersey Filed Nov. 2, 1959, Ser. No. 850,405 5 Claims. (Cl. 12S-290) This invention relates to absorbent pads and covers therefor and more particularly to absorbent pads having warp knit fabric covers.

Absorbent pads, such as sanitary napkins, have been provided with warp knit fabrics to cover and confine the absorbent components of the pad and to provide tabs which extend beyond the absorbent components for attaching the pad in position on the =body of the wearer. While such knit fabrics have been so used, the various types used heretofore have one or more disadvantages. When subjected to tension in the direction of their warp, knit fabrics of conventional form have a tendency to stretch and to simultaneously neck down transversely, causing the pad covered by the fabric to become squeezed and distorted and thus aifect the pads shape and absorbing characteristics. The stretching of the fabric also often results in its becoming loose whereupon it sags and moves out of contact with the elements covered by the cover. This is undesirable in those applications, as in sanitary napkins, where, for good fluid absorbency and iluid transfer, it is desired to maintain the cover and the inner components in intimate face to face contact. Other types of knit fabrics tend to lose their open-mesh knit structure and to gather and bunch along warps when subjected to warpwise tension, forming groupings of threads which are comparatively stiif and uncomfortable when placed direct- 1y against the body, as in the case of sanitary napkins. Still other fabrics unravel and run when subjected to tensile stresses or when attached by means of a clasp or pin. And others designed to overcome some of the above mentioned disadvantages lack the hand and softness of the type desired in a pad which is to be placed in direct contact with the body.

It is an object of this invention to provide an absorbent product, such as a sanitary napkin, having a cover in the form of an open mesh warp 'knit .fabric capable of Withstanding in a warp-wise direction those tensile stresses normally encountered in use without elongating or stretching appreciably. It is another object of this invention to provide a fabric which has transverse stretch lso that when it is applied to the other components forming an absorbent pad, a smooth and intimate contact between the cover and the other components may tbe obtained. It is `another object of this invention to provide an absorbent pad having 'a warp knit cover which does not neck down appreciably when subjected to tension in the direction of its warp, which is soft, which has good hand and which is comfort- 'able when placed in contact with the body of the wearer. It is a furtherobject of this invention to provide an absorbent pad and cover therefor which is of open-mesh knit construction, which has good tensile strength, and which does not unravel and run continuously in a walewise direction when attached in position as by pinning or being secured to a clasp. It is a still further object of this invention to provide an absorbent pad and a knit fabric cover therefor which tends to retain its open mesh structure Vwhen subjected to tension.

The foregoing :and other objects of the invention may be accomplished =by providing a warp knit fabric, preferably hydrophobic, having threads in a back warp in the form of spaced, substantially parallel loops or chain links extending in a Wale-wise direction and threads in a front yvarp extending in a course-wise direction alternately deflected left and right with respect to the back warp and 3,339,549 Patented Sept. 5, 1967 ICC forming looped stitches which are engaged in between adjacent back warps in interlacing relationship with loops of adjacent threads in the front Warp similarly arranged. Each thread passes through a loop in a back Warp in one direction and then returns through another loop in the same warp in the opposite direction and then forms an interlacing loop with an adjacent, similarly looped thread in between the said back warp and an adjacent back warp. After passing'alternately back and forth through loops in a b ack warp, the thread is deflected back again through the back warp and is then passed through the loops of one or more adjacent back warps. By alternately threading the threads in the front warp through one and then through more than one adjacent back warps, and also by staggering the arrangement of the interlacing loops in some of the wales, continuous running of the `fabric in a Wale-wise direction is eliminated. In addition, due to the nature of the weave, an open mesh fabric having good softness and good hand is obtained. When such a fabric is subjected to tension in the direction of its back warp, the threads, particularly the threads in the front warp, do not slide and bunch up on the back warps, but instead tend to remain in position and retain the net-like open mesh construction of the fabric.

Reference is made to the accompanying drawings where- 1n:

FIG. 1 is a perspective view of a sanitary napkin incorporating the invention;

FIG. 2 is a sectional view of FIG. 1 taken along lines 2 2;

FIG. 3 is a view, on a greatly enlarged scale, of the preferred form of fabric incorporating the invention and illustrates the knit pattern of the fabric; and

FIG. 4 is a conventional diagrammatic view of the stitch pattern of the fabric of FIG. 3.

Referring to FIG. 3, there is shown a two-bar open mesh tricot knit fabric 1 having spaced, substantially parallel back warps 2, 2', 2, etc., of threads in the form of loops or chain stitches and a front warp of threads which are deflected left and right through the back warps. Referring to thread a which forms part of the front warp, beginning at b, the thread extends upwardly and to the left, and is then reversed upon itself to form a loop c to the left of back warp 2 in the space 3 in between Warp 2 and the adjacent back warp 2', spaced to the left thereof. After forming the loop, the thread passes to the right through loop d in the back warp 2 and then extends upwardly and to the right and is then reversed upon itself to form another loop e on the right side of the warp 2 in the space 4 between the warp 2 and the adjacent back warp 2" on its right. After forming the loop e on the right side of warp 2, the thread is passed back to the left through loop f in warp 2 adjacent to and above the loop d through which it was first passed. The thread then continues through loop f to and through a loop g in the adjacent warp 2 on the left of warp 2. After so extending, the thread is reversed upon itself to form a loop h in the space 5 in between the said rst adjacent back warp 2 and the next adjacent back warp 2" on the left of warp 2 and is then passed through `a loop i in warp 2 adjacent to and above the loop g -iirst passed therethrough. The thread then continues to warp 2 and is threaded through loop k in warp 2 above loop f and is returned upon itself to form a loop m between the said warp 2 and the warp 2" on the right thereof. The thread then is passed through loop n in warp 2 adjacent to and above loop k and the pattern repeated with the thread being deflected transversely and alternately through adjacent loops of single back warps and thence through the loops in adjacent back warps. Each of the loops formed by the threads in the front warp are interlaced with similar loops formed by similar threads likewise arranged with respect to -adjacent back warps.

The looping and defiecting of threads forming the front warp in the manner described above provides a pattern wherein the loops formed by thread a in space 4 on the right of warp 2 are arranged in a regular and continuous pattern. However the loops formed by thread a on the left of warp 2 are staggered in a Wale-wise direction. Loop c formed on the left of warp 2 is in the space 3 in between warp 2 and warp 2 on the left thereof. The next loop formed by thread a on the left of w-arp 2 is loop I1 in space 5 between warp 2 and 2"', and not in space 3 as in the case of loop c. This pattern of interlaced loops on the left of warp 2 provides a Wale which will not run continuously in a Wale-wise direction.

Continuous running of the fabric in space 4 between warp 2 and warp 2 is prevented because the thread a' on the right of thread a extends across warp 2 and warp 2, in the same manner that thread a extends across warps 2 and 2'. A stitch pattern for providing such a fabric is illustrated in FIG. 4 wherein the stitch pattern for the back warp is O-l, l-O, and the front warp l-0, 3 4, l-O, 6-7 with the threading of each bar being 1 in 2 out.

If the fabric starts to run in the direction of a Wale, the run does not continue throughout the Wale because the interlacing loops are not in continuous :arrangement throughout every Wale, or because adjacent threads forming the front warp extend across those wales having interlacing loops in continuous arrangement. Referring to FIG. 3, if the fabric starts to run in any particular wale, certain of the loops in the Wale become unlaced down the Wale. However, because there is not a continuous series of loops throughout certain of the wales, or because adjacent looped threads extend across wales, the run is stopped las soon as the run encounters one of the threads extending across the Wale in which the run occurs. Further, if the fabric runs, the threads forming the front warp do not group around the back warps because they are not looped around them, but instead extend through the back warps and are interlaced with :adjacent looped threads. Consequently, the fabric tends to retain its soft, open mesh structure because the interlaced loops are engaged with each other between the back warps and not with the back warps themselves.

If desired, the fabric may be so knit that the looped threads are deflected to each side of the back warps in a uniform manner, as for example in the manner illustrated in the drawings in spaces 3 and 5. Alternatively, the knit may be of the type to the right of warp 2 in space 4, with the threads from adjacent front warps extending across space 4 to prevent continuous running. The fabric illustrated combines both features.

The fabric is especially suitable -as a cover for an absorbent pad, such as a sanitary napkin. Referring to FIGS. l and 2, a sanitary napkin 6 having an elongated, absorbent core 7, which may be of any suitable form and material, such as comminuted wood pulp fibers, tissue paper, wadding,cotton, :and the like, is provided with a cover of the fabric 1 in the form of an envelope wrapped around the core and extending beyond the ends of the core to provide attaching tabs 8. The fabric is so arranged with respect to the core that the back warps 2, 2', 2', etc., extend in the direction of the length of the core. In view of the nature `of the knit of the fabric, when the fabric is subjected to tension in a lengthwise direction, i.e., in the direction of the back warps 2, 2', 2, etc., as when the napkin is attached in position by pinning or securing the tabs to clasps, the fabric sustains the tensile stresses imposed due to its construction and does not lengthen or elongate in this direction, thus permitting the napkin to be maintained in the desired intimate contact with the body of the wearer. The fabric, due to its elasticity in a transverse direction may be maintained in intimate and conforming contact with the absorbent core. When the cover is applied to the pad during manufacture, it may be stretched slightly in an outwardly direction transversely to the direction of the back Warp and then released to provide a conforming iit with the core. When the fabric is subjected to tension in a lengthwise direction, the fabric does not neck down but instead retains its original open mesh knitted form, thus providing conformability of the fabric to the core. Due to its Iopen mesh knit structure, iiuids placed on the surface of the fabric rapidly penetrate through the open mesh and are absorbed by the absorbent core below.

The fabric also has a high degree of softness due to its ability to retain essentially its knitted form when subjected to tension in the direction of the back warps. The threads in the front warp which have the interlacing loops do not slide and gather or group along the back warps but instead are retained in their relatively fixed relationship with respect to each other, thereby maintaining the open mesh knit structure.

The pattern of alternating interlacing loops illustrated in the drawings is one wherein the threads of the front warp are alternately deflected back and forth through a single back warp and thence alternately back and forth through the single back warp and adjacent back warps in a repeat pattern. If desired, the arrangement 0f the looped threads may be modied in various ways as by passing through two and three adjacent back warps and then forming the interlacing loops instead of passing through one 4and two back warps in the manner illustrated. Other alternatives include stitch patterns wherein the looped threads pass through one back wrap, and then through three or four, or through two back wraps and then through three, etc. Examples are stitch pattern with the back warp being O-l, 1-0, the front warp being l-O, 3-4, l-O, 9-10; a back warp being (l-l, 1-0 and the front warp being 1 0, 3-4, l-O, 3-4, 1-0, 6-7; a back warp being 0-1, 1-0 and a front warp being either 7-6, 12-13, 7-6, l-O, or 3-2, 1-0, 5-6. The arrangement desired is one wherein the threads in the front warp form a staggered, interrupted or intermittent arrangement of interlaced loops in wales or where the threads forming the interlaced loops extend across wales which would ordinarily split.

A fabric incorporating the invention and suitable as a wrapper for a sanitary napkin may be made on a conventional two-bar tricot machine of any width, preferably 28 gauge, with the guide bars partially threaded in the manner noted above. The fabric may be made from low twist multi-filament threads of synthetic fibers having a denier of from about 20 to about 75 and so knit as to provide from about 15 to about 4() yards per pound. A fabric found acceptable is one knit from low twist 55 denier acetate threads having twenty-two multi-filaments and yielding 23 yards 4of fabric per pound of threads.

The fabric may be made lighter, i.e., increase the number of yards per pound of material, by decreasing the denier of the thread or by increasing the size of the openings in the fabric. For heavier fabrics yielding about 15 yards per pound, a lower denier thread, e.g., approximately '75, may be used; for a-lighter fabric, yielding about 40 yards per pound, a lighter denier may be used, e.g., 20.

The softness and the hand of the fabric is due essentially to the stitch pattern and is fairly constant with threads of different deniers, although variations in softness and hand may be varied somewhat through the use of threads of different materials lor by using threads which contain smaller or different numbers of filaments. For the same denier thread, softer threads may be obtained by using a greater number of filaments. The twist of the thread also inuences the softness of the fabric. It is therefore preferable to use threads with as low a twist as is practical and consistent with manufacturing operations.

The fibers used to form the fabric are preferably hydrophobic to minimize staining on the surface of the cover through absorption of uid and transmission along the threads by wicking and capillarity. Most synthetic fibers, such as rayon, nylon, acetate, and the like are inherently hydrophobic and are especially suitable. However, hydrophyllic fibers, such as cotton fibers, may be used and, if desired, provided with a finish to impart hydrophobic properties, such as by finishing with mineral oil or mineral oil and a nonionic detergent.

The fabric may be knitted to the width desired to provide a cover for a sanitary napkins in which case the fabric may be provided with selvages to minimize ragged edges. A suitable stitch pattern for a fabric approximately seven inches wide made from 5S denier multi-filament acetate thread and having a selvage is 0-1, 1-0 in the back warp and 1-0, 0-1, 1-0, 0-1, (1-0, 3-4, 1-0, 6-7) (69), 1-0, 0-1, 1-0 in the front warp. However, the fabric may be knitted to wider widths and subsequently slit into the Width desired.

It is apparent that numerous variations and changes may be made in the foregoing illustrative embodiments without departing from the scope of the invention.

What is claimed is:

1. A sanitary napkin comprising an absorbent core, an open mesh warp knit fabric cover around said core, the ends of said cover extending beyond the ends of the core forming attaching tabs, said cover comprising two sets of warps, one of said sets being in the form of a plurality of spaced, parallel, knitted loops extending in the direction of said tabs, the other of said sets being in the form of a series of threads deflected left and right through said parallel set, the forming loops between adjacent parallel warps, the loops of said deflected threads being interlaced with loops of adjacent deflected threads, some of said interlaced loops being disposed in an interrupted manner along the wales of the fabric.

2. A sanitary napkin comprising an absorbent core, an open mesh warp knit fabric cover around said core, the ends of said cover extending beyond the ends of the core forming attaching tabs, said cover comprising two sets of warps, one of said sets being in the form of a plurality of spaced, parallel, knitted loops, extending in the direction of said tabs, the other of said sets being in the form of a series of threads deflected left and right through said parallel set, and forming loops between adjacent parallel warps, the loops of said dellected threads being interlaced with loops of adjacent dellected threads, a portion of said interlaced loops lbeing disposed in continuous arrangement in some of the wales in said fabric, the other of said loops being disposed in an intermittent arrangement in other wales, the threads forming said interlacing loops extending across said wales having loops formed iu continuous arrangement.

3. A sanitary napkin comprising an absorbent core, an open mesh warp knit fabric cover around said core, the ends of said cover extending beyond the ends of the core forming attaching tabs, said cover comprising two sets of warps, one of said sets being in the form of a plurality of spaced, parallel, knitted loops extending in the direction of said tabs, the other of said sets being in the form of a series of threads deflected left and right through said parallel set, said threads forming said loops extending, in a repeat pattern, back and forth across a single warp, and back and forth across said single warp and an adjacent warp, and forming loops between adjacent parallel warps, the loops of said dellected threads being interlaced with loops of adjacent deflected threads.

4. A sanitary napkin comprising an absorbent core, an open mesh warp knit fabric cover around said core, the ends of said cover extending beyond the ends of the core forming attaching tabs, said cover comprising two sets of warps, one of said sets being in the form of a plurality of spaced, parallel, knitted loops extending in the direction of said tabs, the other of said sets being in the form of a series of threads dellected left and right through said parallel set, and forming loops between adjacent parallel warps, the loops of said deected threads being interlaced with loops of adjacent deflected threads, the threads forming said interlacing loops extending across the spaced parallel warps in an intermittent pattern.

5. A sanitary napkin comprising an absorbent core, an open mesh warp knit fabric cover around said core, the ends of said cover extending beyond the ends of the core forming attaching tabs, said cover comprising two sets of warps, one of said sets being in the form of a plurality of spaced, parallel knitted chains extending in the direction of said tabs, the other of said sets being in the form of a series of threads deflected left and right through said parallel chains, said threads extending, in a repeat pattern back and forth across a single chain, and then back and forth across said single chain and an adjacent chain, and forming loops between adjacent parallel chains, the loops of said deffected threads being interlaced with loops of adjacent deected threads.

References Cited UNITED STATES PATENTS 811,704 2/ 1906 Dix 12S-290 903,895 11/ 1908 Schulz 128-290 1,829,231I 10/ 1931 Mergentime 66-170 2,433,279 12/ 1947 Johnson 66-195 2,535,376 12/1950 Thompson 66--195 3,208,451 9/ 1965 Porter et al. 12S- 290 FOREIGN PATENTS 787,949 12/ 1957 Great Britain. 803,787 10/ 1958 Great Britain.

RICHARD A. GAUDET, Primary Examiner.

CHARLES F. ROSENBAUM, H. B. WHITMORE,

Examiners. 

1. A SANITARY NAPKIN COMPRISING AN ABSORBENT CORE, AN OPEN MESH WARP KNIT FABRIC COVER AROUND SAID CORE, THE ENDS OF SAID COVER EXTENDING BEYOND THE ENDS OF THE CORE FORMING ATTACHING TABS, SAID COVER COMPRISING TWO SETS OF WARPS, ONE OF SAID SETS BEING IN THE FORM OF A PLURALITY OF SPACED, PARALLEL, KNITTED LOOPS EXTENDING IN THE DIRECTION OF SAID TABS, THE OTHER OF SAID SETS BEING IN THE FORM OF A SERIES OF THREADS DEFLECTED LEFT AND RIGHT THROUGH SAID PARALLEL SET, THE FORMING LOOPS BETWEEN ADJACETN PARALLEL WARPS, THE LOOPS OF SAID DEFLECTED THREADS, SOME OF SAID INTERLACED LOOPS BEING DISPOSED IN AN INTERRUPTED MANNER ALONG THE WALES OF THE FABRIC. 